U.  S.  DEPARTMENT  OF  AGRICULTURE, 

l;i  UK.W  OF   PLANT  [NDUSTRY— Circular  No.  39. 

B     I     GALLOWAY,  Chief  of  Bureau. 


THE  DECAY  OF  CABBAGE  IN  STORAGE: 

ITS  CAUSE  AM)  PREVENTION. 


L.    L.    IIAKTEK, 
A.8SISTAN1    Pathologist,  Cotton  and  Truck   Disease 

I  WVESTIGATIONS. 


••   •     Cll   39    09 


WASHINGTON   :  GOVERNMENT  PRINTING  OFFICE  :  1809 


UNIV  OF  Fl  l_i£ 
DOCUMENTS  DEPT. 

*%  *S  S*\ 

-POSITORY 

BUREAU  OF  PLANT  INDUSTRY. 


Chief  of  Bureau,  Beverly  T.  Galloway. 
Assistant  Chief  of  Bureau,  Albert  F.  Woods. 
Editor,  J.  E.  Rockwell. 

Chief  Clerk.  James  E.  Jones. 

[Cir.  39] 
2 


ii.  r  1 


THE  DECAY  OF  CABBAGE  I\  STORAGE:  ITS  CAUSE 
AND  PREVENTION. 


INTRODUCTION. 

The  loss  from  deca)  of  cabbage  in  winter  storage  has  men. 
to  such  an  extent  in  some  districts  in  the  pasl  few  years  as  freqneniSy 
to  make  the  growing  of  this  crop  an  almosl  unprofitable  industry. 
Of  ilif  thousands  of  tons  stored  every  fall  to  supply  the  markets  in 
the  winter,  from  LO  to  50  per  cent  is  losi  annually  from  decay.  Soon 
after  the  cabbage  is  put  in  the  storage  house  many  of  the  outer  leaves 
of  the  heads  turn  black  and  become  soft.  In  order  to  meet  the 
requirements  of  the  market  it  i-  necessary  to  pull  off  several  of  the 
outer  leaves,  thus  reducing  materially  the  size  of  the  head. 

Investigations  into  the  causes  of  the  decay  of  cabbage  in  storage 
and  into  the  mean-  of  preventing  ii  were  undertaken  for  the  purpose 
of  determining  the  factors  contributing  to  this  loss  and  what  prac- 
ticable remedial  measures  can  besl  he  employed  to  reduce  it  to  a 
minimum. 

It  was  accessary  \<<  determine  the  extent  to  which  bacterial  organ- 
isms and  leaf-blighl  were  responsible  for  the  trouble  and  how  tiny 
gained  access  to  the  tissue  of  the  cabbage.  This  investigation 
necessitated  a  stud)  of  the  disease  affecting  cabbage  in  the  fields 
from  which  storage  -lock  was  obtained  and  of  the  methods  of  han- 
dling the  crop  when  being  harvested  and  placed  in  storage  houses. 

A  the  development  of  the  bacteria  and  the  leaf-blighl  which  are 
larger)  responsible  for  the  decay  of  cabbage  depends  on  temperature 
and  humidity,  a  study  was  made  of  the  construction  of  the  houses, 
with  a  \  ieu  to  the  control  of  these  factors  during  the  storage  period. 

These  studies  must  be  regarded  as  preliminary,  undertaken  to 
learn  the  nature  and  importance  of  the  problem.  The  writer  has 
observed  in  the  fields  the  method  of  harvesting  and  storing  cabbage 
during  two  seasons.  Examinations  were  also  made  of  house-  where 
loss  occurred  and  of  those  relatively  free  from  loss.  During  a  period 
of  several  mouth-  the  range  of  temperature  and  the  relative  humidity 
in  such  houses  were  observed. 


is  paper  was  prepared  al  the  request  (     Corbett,  Borticulturisl  .if 

i  Planl  Industry .  after  a  study  of  conditions  in  the  State  of  .New  York. 
Ii  has  reference  especially  to  the  northern  cabbage  districts,  from  New  York  to  Minne- 
sota, where  the  winter  storage  of  this  crop  is  largely  practiced.     It  aim-  men 
diagnose  the  situation  ami  outline  plainly  Deeded  preventives      I'.    T    Gai 

[Cir.  39 J  ;< 


4  THE  DECAY  OF  CABBAGE  IN  STORAGE. 

The  conclusion  has  been  reached  that  cabbage  which  comes  to 
storage  in  good  condition  can  be  preserved  if  the  best  types  of  stor- 
age houses  are  adopted  and  the  temperature  and  humidity  properly 
regulated  by  careful  ventilation,  but  this  is  only  one  phase  of 
the  storage  problem.  Its  complete  solution  is  not  likely  to  be 
reached  until  the  problem  is  taken  up  from  the  field  standpoint  and 
demonstrations  made  of  the  influence  on  keeping  quality  of  methods 
of  culture,  care  in  handling,  time  elapsing  between  harvesting  and 
storage,  etc.  The  Bureau  of  Plant  Industry  has  already  shown  the 
important  influence  of  these  factors  on  the  keeping  of  oranges  and 
other  fruits. 

That,  a  great  improvement  can  be  made  in  the  technique  of  cab- 
bage storage  is  not  to  be  doubted,  but  until  the  time  arrives  when 
funds  for  such  work  are  available  the  suggestions  in  this  circular 
may  assist  cabbage  growers  and  warehousemen  to  reduce  their 
losses. 

FACTORS  CONTRIBUTING  TO  DECAY. 

It  seems  hardly  necessary  to  emphasize  the  point  that  no  diseased 
cabbage  should  go  into  winter  storage.  Diseased  heads  not  only  do 
not  keep  well,  but  they  become  the  source  of  infection  for  healthy 
stock. 

FIELD    INFECTIONS. 

All  three  of  the  diseases  causing  loss  of  cabbage  in  storage  may 
originate  in  the  field.  Black-rot,  so  far  as  known,  always  results 
from  infections  in  the  field.  An  examination  should  be  made  of  all 
cabbages  before  storing,  and  heads  affected  with  black-rot  rejected. 
Frequently  only  very  slight  traces  are  observable,  and  it  is  perhaps 
permissible  to  store  such  heads  for  short  periods.  Their  keeping, 
quality  has,  however,  become  impaired  and  they  should  be  marketed 
early.  Cabbage  that  has  been  frozen  in  the  field  should  either  be 
allowed  to  thaw  and  dry  before  going  into  the  storage1  house  or  be 
rejected  altogether,  as  frozen  cabbage  does  not  keep  well. 

The  soft-rots  are  less  common  in  the  field,  lint  when  they  occur 
are  often  very  destructive.  Special  care  should  be  taken  to  reject 
cabbages  which  show  traces  of  soft-rot  when  brought  in  for  storage. 

Leaf-blight  is  quite  common  in  some  fields,  but  is  usually  confined 
to  flu1  outer  leaves,  which  can  he  removed  before  storing.  This 
disease  is  usually  regarded  as  less  important  than  the  soft-rots,  as 
its  further  development  <an  be  prevented  by  proper  ventilation  of 
the  storage1  house. 

HOUSE    INFECTION. 

If  a  house  has  been  used  for  one  or  more  seasons  for  storage  pur- 
poses and  there  has  been  am  evidence  of  decay,  it  is  a  good  plan  to 
disinfect  the  interior  of  the  building  in  the  fall  before  new  slock  is 
put   in.      The   spores   of   many    fungi    and    bacteria    can    retain    their 

[CIr.  39] 


THE    DECAl     0]     C  \iu;  \i,l.    I  ,\    STORAGE.  5 

vitality  for  a  long  time.  If  the)  are  lefl  in  a  house  thai  lias  qoj 
been  disinfected  From  one  season  to  the  next,  the  newly  stored  crop  is 
exposed  to  infection  whenever  temperature  conditions  are  favorable. 
Spraying  the  walls,  ceiling,  and  benches  with  about  a  half  of  I  per 
cent  solution  of  copper  sulphate1  or  the  application  of  a  whitewash 
alone,  either  of  which  could  be  applied  with  the  usual  spray  pump, 
would  he  cheap  and  practicable.  An  application  of  either  a  copper 
solution  or  whitewash  should  he  made  long  enough  before  the  house 
is  used  for  storage  to  permit  the  wood  to  dry  thoroughly. 

CARELESS    II  \  \  M  INC. 

A  large  proportion  of  the  decaj  in  stored  cabbage  doubtless  origi- 
nates in  bruises  due  to  rough  handling.  Plant  tissues  are  well  pro- 
tected against  decay  so  long  as  they  are  uninjured,  but  any  break  in 
tin1  epidermis  may  serve  as  a  starting  point  of  decay. 

Whole  loads  of  cabbage  have  been  seen  at  the  storage  house  with 
scarcely  a  head  not  bruised  and  torn  from  careless  handling.  Cab- 
hould  he  given  the  same  attention  that  expert  fruit  packers 
give  to  apples.  The  heads  should  never  he  Thrown  into  the  wagon 
when  gathering  in  t he  field  or  t  hrown  from  i  he  wagon  to  the  bin  when 
unloading,  hut  always  passed  from  hand  to  hand. 

ORGANISMS  CONCERNED  IN  DECAY. 

An  examination  of  cabbage  undergoing  decaj  in  storage  shows 
t  hat  t  hree  kinds  of  organisms  black-rot ,  soft-rot ,  and  leaf-blighl  are 
principally  concerned  in  producing  the  injury. 

BLA<  K    R<  •!  . 

Black-rot  is  one  of  the  most  serious  diseases  of  cabbage  in  the  held 
and  is  responsible  for  much  of  the  loss  from  decay  in  storage.  It  is 
caused  by  a  parasitic  bacterium"  which  gains  access  to  the  young, 
growing  plants  through  the  roots  or  through  marginal  infection  of 
the  leaf.  The  bacteria  then  grow  up  from  the  loots  or  down  from 
the  point  of  infection  of  the  leaf,  through  the  fihro-vascular  bundles, 
tot  he  head.  The  black-rot  organism  itself,  under  storage  condil  ions, 
seldom  completes  i  he  destruction  of  the  head,  hut  cabbages  affected 
by  it  are  more  liable  to  attack  by  soft-rot  bacteria  and  by  fungi, 
which  .level.. p  rapidly  under  favorable  conditions.  The  control  of 
black-rot  in  the  field,  therefore,  will  greatly  reduce  the  loss  from 
decay  in  storage. 

Upon  cutting  across  the  stem  or  through  the  leaf  black-rot  can  be 

detected  by   the  black  ring  in  the  woody  part   of  the  stem  and   by  the 

blackening  of  the  veins  of  the  leaves. 


/•  campest  ■     Pam      Erw.  Sra. 


6  THE  DECAY  OF  CABBAGE  IK  STORAGE. 

SOFT-ROT. 

Soft-rot  is  clue  to  a  group  of  related  species  of  bacteria  rather  than 
to  one  species.  The  bacteria  gain  access  to  the  tissue  of  the  leaves 
of  the  cabbage  principally  through  wounds  made  by  careless  handling 
and  by  infection  of  the  stem  and  leaves  previously  attacked  by 
black-rot.  Other  crops,  such  as  carrots  and  turnips,  are  subject  to 
similar  injury.  The  soft-rot  bacteria  as  a  class  are  marked  by  their 
ability  to  destroy  plants  very  quickly  under  favorable  temperature 
conditions.  They  seldom  affect  uninjured  plants,  but  require  a 
wound  or  other  injury  in  order  to  gain  a  foothold. 

LEAF-BLIGHT. 

Leaf-blight  is  due  to  a  fungus"  which  attacks  the  plant  at  any  stage 
of  its  growth  but  is  more  likely  to  develop  on  a  plant  subjected  to 
unfavorable  conditions.  In  the  seed  bed  and  in  the  field,  leaf-blight 
is  distinguished  by  the  dark,  mildewed  spots  it  produces  on  the 
leaves.  In  warm  storage  houses  and  in  the  presence  of  sufficienl 
moisture  it  spreads  very  rapidly  over  the  leaves  and  causes  consid- 
erable loss  from  decay.  The  fungus  can  not  grow,  however,  at  a 
temperature  near  freezing  and  in  the  absence  of  humidity. 

STORAGE  CONDITIONS  NECESSARY  FOR  PREVENTING  DECAY. 

The  most  favorable  results  in  the  preservation  of  cabbage  are 
secured  only  by  the  skillful  regulation  of  the  temperature  and  humidity 
through  daily  attention  to  the  ventilation  of  the  houses.  Tempera- 
ture and  humidity  are  the  most  important  factors  to  be  considered  in 
connection  with  cold  storage.  If  the  proper  temperature',  along  with 
thy  houses,  could  he  kept,  the  organisms  which  cause  the  decay  of 
cabbage  would  be  held  in  check.  In  other  words, the  organisms  would 
not  develop  if  the  temperature  could  be  held  at  about  one  degree 
above  the  freezing  point.  Since  it  is  impossible,  owing  to  periods  of 
warm  weather  in  the  winter,  to  maintain  such  a  uniform  tempera- 
ture, humidity  plays  an  important  part.  Decay  would  he  much  less 
in  a  house  with  high  temperature  and  little  humidity  than  in  a 
house  with  high  temperature  and  a  relatively  large  amount  of 
humidity. 

Temperature  and  humidity  must  largely  he  controlled  by  a  well- 
planned  system  of  ventilation  with  outdoor  air.  When  a,  long 
period  of  very  cold  weather  makes  it  impossible  to  keep  the  tempera- 
lure  at  a  little  above  freezing,  one  or  two  stoves  can  he  put  in  the 
house,  which  would  also  materially  reduce  the  humidity.  Moisture 
should    not    he   allowed   to   condense   on    the   cabbage,    and    not    very 

"  Alternaria  bri  Berf      :  ice. 

[Cir.  :i'.i] 


I  III  DECAY  OF  CABBAGE  IN  STORAGE.  7 

much  on  the  walls  and  ceiling.  Whenever  moisture  is  condensed  on 
the  cabbage  the  house  is  in  bad  condition  and  should  be  dried  al  once, 
even  if  a  stove  must  be  put  in  and  the  temperature  raised.  After 
drying,  the  temperature  could  be  reduced  by  admitting  outside  air 
through  the  doors.  When  stoves  arc  put  in  houses  'arc  should  be 
exercised  thai  too  much  smoke  docs  not  escape  inside,  as  this 
would  probably  injure  the  sale  of  the  cabbage. 

It  is  only  in  extreme  eases  that  the  proper  condition  of  the  house 
can  not  be  maintained  by  ventilation  with  outside  air.  Cabbage  is 
constantly  giving  off  moisture  unless  frozen,  [f  a  house  is  kepi  closed, 
the  relative  humidity  will  increase  until  the  air  is  saturated.  Any 
reduction  in  temperature  would  then  condense  the  moisture  on  the 
cabbage  and  the  walls  of  the  house.  It  is  believed  that  the  house 
should  be  opened  every  day  except  when  warm  or  very  damp.  The 
house  should  be  opened  for  ventilation  during  clear  weather  when 
the  air  is  dry,  and  at  a  time  of  day  when  the  temperature  is  near  the 
freezing  point.  The  temperature  of  the  house  would  then  he  little 
changed,  and  the  relative  humidity  inside  would  he  reduced  to  that 
of  t  he  air  outside. 

In  a  storage  house  of  a  capacity  of  about  1,600  tons,  in  the  State 
of  New  York,  a  system  of  ventilation  has  been  installed  which  con- 
sists of  pipes  running  through  the  building,  through  which  the  air  in 
the  house  i>  drawn  by  a  fan  run  by  electric  power.  The  pipes  grad- 
ually decrease  in  size  as  they  ramify  through  the  building.  It  is 
claimed  that  h\  such  a  system  the  air  can  he  changed  in  the  whole 
building  in  twenty  minutes.  The  owner  makes  h  a  practice  to  change 
the  ail-  once  every  twenty-four  hours  unless  the  temperature  isvery 
high  and  the  air  humid.  His  stock,  when  seen  in  midwinter,  was  in 
excellent  condition.  No  decayed  heads  nor  any  moisture  condensed 
on  t  lie  cabbage  were  found. 

CONSTRUCTION  OF  STORAGE  HOUSES  TO  PREVENT  DECAY. 

Since  the  objeel  in  storing  cabbage  is  to  keep  the  house  near  the 
freezing  point  and  as  dry  a-  possible,  the  construction  of  the  house  is 
important  only  in  so  far  as  it  contributes  to  that  end.  It  is  probable 
that  the  best  t\  pe  of  house  is  made  of  hrick  or  stone,  the  walls  being 
Is  to  ■_'  l  inches  in  thickness.  Thick  walls  are  essential,  since,  being 
less  affected  h\  varying  temperature-,  they  make  it  possible  to  keep 
the  interior  cool  during  a  period  of  warm  weather.  The  roof  should 
he  made  of  the  usual  sheathing  and  shingles.  It  would  he  preferable 
to  have  the  sheathing  run  from  the  comh  of  the  roof  to  the  eav< 
which  would  enable  the  water,  if  frost  forms  and  melts  on  the  inside, 
to  run  to  the  side  of  the  building  instead  of  dripping  on  the  cabbage. 

|(  ir.  39] 


8  THE  DECAY  OF  CABBAGE  IX  STOKAGE. 

A  house  100  feet  in  length  should  have  at  least  four  ventilators  on 
the  comb,  which  would  permit  outside  air  coming  in  from  below  to 
drive  the  warm,  damp  air  out  through  the  top.  A  building  made  of 
wood,  with  the  walls  two  or  three  boards  thick,  though  not  as  good 
as  a  stone  house,  has  in  many  cases  given  good  results. 

METHODS  OF  STORING  CABBAGE. 

There  are  two  common  methods  of  storing  cabbage — in  bins  and 
on  shelves.  Both  have  their  advantages.  Most  storage  men  prefer 
to  use  bins,  because  in  this  way  a  larger  tonnage  of  cabbage  can  be 
stored  per  cubic  yard  of  space.  Others,  however,  store  on  shelves, 
believing  that  the  cabbage  keeps  better. 

The  aeration  in  bins  is  at  best  not  good,  and  for  that  reason  shelves, 
where  the  heads  are  only  two  or  three  deep,  are  preferable.  When 
stored,  the  cabbage  should  be  placed  with  the  stem  end  upward,  so 
that  all  water  dripping  from  the  ceiling  or  any  moisture  that  may 
condense  on  the  leaves  will  more  readily  run  off. 

CONCLUSIONS. 

Soft-rot  and  leaf-blight  are  the  immediate  causes  of  the  decay  of 
cabbage  in  storage.  The  organisms  causing  these  decays  gain  access 
to  the  tissues  of  the  leaves  through  wounds  made  by  careless  handling 
and  also  by  following  up  the  fibro-vascular  bundles  which  have  been 
previously  killed  by  black-rot. 

Diseased  or  badly  bruised  cabbage  should  not  be  stored.  The 
most  important  factors  in  the  keeping  of  cabbage  in  storage  are  tem- 
perature and  humidity.  Water  should  not  be  allowed  to  accumu- 
late in  drops  on  the  cabbage,  and  if  it  does  immediate  steps  should 
be  taken  to  dry  the  cabbage,  either  by  admitting  air  from  the  outside 
or  by  the  use  of  stoves  inside.  Stoves  should  not  be  used,  however, 
if  it  is  possible  to  obtain  (he  same  results  by  using  cold,  dry,  outside 
air.  Houses  should  be  opened  and  ventilated  every  day  except 
when  the  air  is  dam])  and  warm.  Cold  weather,  when  the  tempera- 
ture is  at  about  the  freezing  point,  is  best  for  ventilation. 

The  construction  of  houses,  the  methods  of  storing,  etc.,  are  impor- 
tant in  so  far  as  they  contribute  to  the  keeping  of  dry  houses  and  the 
maintenance  of  a  uniform  temperature  slightly  above  freezing. 

Approved: 

James  Wilson, 

Secretary  of  Agriculturt . 

Washington,  1).  C  September  9,  1909. 

[Cir.  39.] 


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